The present invention relates to an adjustable routing clamp assembly for use in trucks for retaining bundles of elongated members, such as wiring harnesses, air brake hoses, fuel hoses, etc., to the truck frame at various points therealong. More particularly, the routing clamp of the invention includes an extension element to be attached to the frame having a plurality of slots spaced thereon and a tie strap engaged to the extension at a first slot on one side of the bundle and disposed to wrap around the bundle and engage the extension at a second slot displaced from the first slot by the width of the bundle, with a toothed keeper element used to maintain the strap in engagement with the bundle and extension element, thereby providing an adjustable clamp assembly capable of accommodating engagement of various size bundles by using different slots along the extension element while providing a stable mounting of the bundle to the frame.